Ever since the public discussions on the ozone-damaging potential of certain chlorofluorocarbons there has been intensive work in the field of alternative propellants for pharmaceutical metered-dose aerosols. It has been known since the early 1990s that the propellant gases TG 227 ea or TG 134 a may be used as alternative propellant gases for aerosols.
It has now been found that, surprisingly, propellant gas formulations with suspended particles of active substance and TG 227 ea or TG 134 a as propellant can be stabilised if the propellant gas or propellant gas mixture contains a certain amount of water.